The research proposed is directed toward the study, on a molecular level, of a set of coordinately controlled genes in a eukaryote. These are the ribosomal protein genes of Drosophila melanogaster. This work will include (a) the study of the kinetics of synthesis of the ribosomal proteins with respect to each other and to the ribosomal RNA's, particularly in reference to mutants containing deletions of ribosomal RNA genes; (b) the study of the location of some of the mRNA's coding for these proteins, both on the chromosomal level and on long DNA strands; and (c) further developmental studies on the developmentally controlled initial synthesis of these proteins. The results of this study will be used to evaluate the timing of expression of the various ribosomal protein genes and their chromosomal location with a view toward understanding the molecular basis for regulation of this set of essential protein genes in a eukaryote.